Linux

The flowchart is as follows:

LibreOffice or OnlyOffice for desktop apps (no, they are not Microsoft apps, but yes they use Microsoft formats and can edit and save Microsoft documents/spreadsheets/etc). OnlyOffice is the closest of the two to the Windows experience.

If you really aren't open to using alternative software (which is strange given that you're using Linux), then the web apps exist. I've heard they're really close to the actual desktop suite, though I don't have any interest in ever using them as we have very good free and open source alternatives available (see above).

If the web apps don't cut it for you, then you can run the official apps in a VM, or maybe through WINE. Here's the WINE DB page for Microsoft Office, which lists various Office versions and their level of compatibility through WINE.

~~Copilot will likely not be possible to secure on Linux in a standalone desktop app (unless someone somewhere hacked something together through Electron to use a web version)~~. Another user said that Copilot is available inside Microsoft Edge, so I suppose you could install that, though I'd highly discourage that. Reliance on LLMs is quite frankly a plague to society, and often feeds incorrect, biased, or purely fabricated responses, as LLMs merely attempt to predict what word is most likely to occur next based on a set of training data, none of which was vetted for accuracy, racism, zionism, sexism, etc. LLMs like copilot do not have any form of intelligence, and do not understand what they are saying. I highly recommend you just use a search engine in your browser, because it'll feed you the same info all the LLMs were trained on anyway.

OneDrive recently received native support in GNOME, so I think you should be able to access it in your settings under accounts/connected services (whatever GNOME calls it nowadays)? I've never tried to use it, so other people will know better than I will there, but it should be possible to use.